They squeal, they wail, they yelp and, according to consumer advocate Ralph Nader, they are not necessary. They may even be dangerous when they pierce the eardrums of noonday lunchers and awaken babies in the night, he says.

Nader, who has taken on such behemoths as General Motors and the federal government, this time has set his sights on the use of sirens. He is concerned specifically with police, fire and rescue sirens in Washington, which he calls "Siren City, U.S.A."

Siren noise is "a nuisance to office workers and residents, and a physiological hazard to many pedestrians and occupants of the (offending) emergency vehicle," Nader claims in a current report.

Police officers, firefighters and ambulance drivers, however, defend the sirens as essential to deal with the District's congested rush hour traffic. They say that safeguards and self-regulation prevent abuse by the drivers. Nader, however, says, "Two out of four of these (siren runs) are phony. They just don't want to wait for a red light."

Nader's report concludes that sirens, for all their ill effects, do not serve their primary purpose, which is to warn drivers and pedestrians that an emergency vehicle is approaching. He says that "a person in a car with the windows rolled up and the air conditioner on and the radio tuned in will not hear the siren" until it is as close as 50 feet.

Both Nader and area emergency vehicle drivers agree on that point. But while Nader sees insulated cars as one of the reasons for banning sirens - or at least toning them down - the emergency vehicle drivers see that as the reason to make sirens louder.

"In my opinion," says Peter Huntemann of Huntemann's Ambulance Service, "they're not loud enough. The more noise you make, the more people get out of your way."

Battalion Chief Richard M. Upshur of the fire department says, "The law is not brought out to the people about yielding the right-of-way." Upshur suggests a program to educate the public, possibly using spot television commercials.

Fire engines with traditional sirens use them only "intermittently" Upshur says, and not at all when returning from a fire. Also, fire truck drivers are not allowed to use their sirens at hospitals, theaters "or any place of public gathering" except office buildings.

Police department officials say that abuse is impossible because every siren run is logged and recorded. Officers can use their sirens only on an assigned "code one" run on instructions from the communications dispatcher. "Code one" calls are for the most serious situations, such as an officer in trouble. A police officer may use a siren without such authorization in rare emergencies, but he must report it to the communications dispatcher "at the first available opportunity." And even then, the use of the siren is recorded in the log book.

Nader says that sirens, even when used legitimately, constitute a health hazard. "The sound secreted by an emergency vehicle siren . . . adversely affects the physiological processes of the emergency vehicle operator," Nader the report says. "His blood pressure and heart and respiration rate all increase" and the driver has "heightened anxiety" the report says.

Besides being a hazard to the driver, Nader says, the patient in the back of an ambulance with siren wailing may suffer increased heart rate and may feel that his injury is worse than it really is.

"I've never had any patient or any family complain about the noise in the back of an ambulance," says Huntemann, a driver for 30 years. He said that in all those years "siren noise has never hurt the patient. What has hurt the patient is accidents caused when people don't hear the ambulance coming."

Another driver, Sterling W. Hackett Sr. of Economy Ambulance, agrees. "We appreciate Mr. Nader's concern, but Mr. Nader is not responsible for those patients. I think Mr. Nader should mind his own damn business," Hackett said. He added that the one minute saved by the siren "can make the difference in a person living or dying."

"They are so difficult and adamant, and they are trying to wrap the safety mantle around themselves," Nader said. "It (the siren) is simply not needed medically except in the rarest of circumstances."

Instead, Nader said, the solution is for the ambulance crews to be trained to stabilize emergency patients at the scene, thereby obviating the need for a high-speed run back to the hospital.

That was the theory behind the establishment of the District's paramedic program two years ago. Both Virginia and Maryland launched earlier studies of on-the-spot medical care. Many doctors agree that better medical care at the scene is more important than rushing the patient to a hospital emergency room.

"It has become the mode to use red lights and sirens even in non-critical conditions," said Dr. Sander Mendelson, a cardiologist who has researched emergency patient care for the District. ". . . all the jostling around may be more dangerous to the patient." He said the patient is "better off with trained persons with good equipment and radio communication to the hospital than with just rushing with red light and siren."

Nader's suggestions for alternatives to the siren include:

Switching to the quieter, European-style air siren, more of a buzzer than a siren.

Shielding the siren speakers to prevent the noise from traveling upwards to surrounding office buildings. "There must be 40,000 people who curse these things out daily," Nader said from his office on Connecticut Avenue at K Street.

Encouraging the use of a public address system atop ambulances and emergency vehicles, so the driver could direct traffic out of his way.

Encouraging the emergency vehicle to use the vehicle horn "when a simple toot would do the job. It is quieter, more familiar and less nerve-racking," Nader says.

Establishing a "quiet hour" banning sirens between 11 p.m. and 7 a.m. Most emergency vehicle drivers seemed hostile to this idea too, for liability reasons in case of an accident. That is why the city of Alexandria vetoed a proposal for a similar siren "quiet hour" in 1973.

Investigating an Emergency Traffic Control system in use in two Pennsylvania cities. With that system, in which the towns of Erie and York have eliminated sirens, the emergency vehicle driver can trigger all traffic lights from his own dashboard and create a "wave" of green lights ahead of him.

That system is credited with cutting the number of accidents involving emergency vehicles by a third. The system cost $463,000 to install, and $20,000 a year to maintain, according to a report prepared for Montgomery County's Noise Control Advisory Board.

Most experts interviewed agreed that such a system for a city the size of Washington would not be cost-effective, at least for the time being.